Current Project: Potassium Needs of Alfalfa
Research Team:
Quirine Ketterings, Karl Czymmek (PRODAIRY), Greg Godwin, Sheryl Swink, Sanjay Gami, Peter Barney (Barney Consulting), Colleen Daly and Brian Boerman (ACS), Stephen Canner, Janice Degni, Mike Stanyard, James Kingston (Cornell Cooperative Extension), Eric Young (Miner Institute), and undergraduate interns/students.
Funding Sources:
New York Farm Viability Institute (NYFVI), Federal Formula Funds, Northeast Sustainable Agriculture Research and Extension (NESARE), International Plant Nutrition Institute (IPNI).
Field Protocols:
- Alfalfa and Potassium Protocol 2010 (3-28-2011).
Publications:
- Ketterings, Q.M., G. Godwin, J. Cherney, and K. Czymmek (2011). Effect of manure, compost and potassium application on alfalfa yield, potassium content, and soil test potassium in Aurora, NY. What’s Cropping Up? 21(4): 8-12. (12-16-2011).
- Ketterings, Q.M., G. Godwin, J. Cherney, and K. Czymmek (2011). Comparison of tissue and whole plant potassium for alfalfa. What’s Cropping Up? 21(4): 13-15 (12-16-2011).
- 2010 Potassium Needs of Alfalfa Summary Report (2-25-2011).
Popular Press Articles:
- Project Examines Potassium Dynamics of Alfalfa and Soil (NMSP Impact Statement; 8-21-2011).
Introduction
While K fertilizer cost has decreased from recent all-time highs of $0.80/pound to currently $0.40/pound, K remains an expensive macro-nutrient. Alfalfa is a large remover of K (56 lbs K2O per ton DM) and with an alfalfa forage production of 680,000 acres and average per acre yield of 3.6 ton reported for 2009, crop removal amounts to 116.5 million pounds of K2O. If this K had to be returned to the soil as fertilizer K, it would represent a price tag exceeding $46.6 million dollars (about $70 per acre alfalfa cropland). Potassium removed by crop harvest can be “returned” as manure K and/or fertilizer or be supplied by the soil. Soil K supply is large for clay soils and fairly low for sandy soils but all soil will supply K to crops as soil minerals weather (break down) over time, reducing the need for K supplementation from manure or fertilizer. Manure, when applied to meet N needs for corn in a corn-alfalfa rotation, supplies large amounts of K during the corn years, increasing soil test K levels which benefit the alfalfa in the following years, and many dairy producers are comfortable with K levels going into the first couple years of alfalfa of the rotation. However, producers and agricultural advisors are reluctant to not use K fertilizer for older (3rd, 4th year) alfalfa stands out of concern for reduced yield and/or winter kill.
Producer questions addressed in this project are: (1) is K applied with manure in corn years sufficient to bridge alfalfa years in the rotation, and (2) what tools could be used to reliably identify if extra K is needed. For K management, three approaches are commonly used in New York: (1) K removal, (2) soil test K, and (3) K saturation-based methods.
Project Setup
In 2001, a large-scale long-term corn-alfalfa rotation study was initiated at the Musgrave Research Farm in central NY. Corn silage was grown for 5 years on calcareous soils under N and P-based manure and/or compost management as well as 6 rates of N fertilizer only. The field was then rotated to alfalfa. Results indicated a substantial increase in soil test K levels in the manure and compost plots during the corn phase while in the fertilizer-only plots soil test K levels remained constant .
In 2006, alfalfa was seeded and in 2007 six K application rates were implemented (fertilizer-only plots with soil test K levels classified as medium) to see if the alfalfa in the fields without the manure or compost history would respond to the extra K. No compost or manure addition took place under the alfalfa years.
In addition, in 2009-2011, on-farm trials were conducted at 30 locations throughout the state. Each site consisted of four replications of two treatments: with and without addition of 350 lbs K2O/acre directly after 1st cutting. Sites were sampled for yield, tissue K, soil test K, and at the final harvest in 2011 (4th cutting) a stand composition was done (alfalfa, grass, broadleaf weeds).
Results to Date
The data from the research farm rotation study (at Aurora) indicate that the annual manure and compost additions at both N and P-based rates during corn silage production years provided sufficient K to meet crop needs for the following five alfalfa years. When N-based rates of manure were applied during the corn years, soil test K levels were elevated at the start of the alfalfa portion of the rotation and remained elevated over all other treatments for the five years of alfalfa. Soil test K levels were back to 2006 baseline levels for the other three organic amended treatments. These results indicate that corn alfalfa rotations can be managed without K addition during the alfalfa years in a manure or compost context. For plots without a compost or manure history, soil test K levels were maintained over the years without K fertilizer addition and despite plant K levels below 2% the alfalfa did not show a yield increase with K fertilizer addition suggesting the soil’s annual K supply was sufficient to sustain a 4 tons/acre per year yield at this location. Regular soil testing is the best way to monitor fields for responsive conditions to avoid yield losses or unnecessary expenses and unnecessarily high forage K levels that can lead to other problems. The yield increase in the plots with the manure or compost histories over plots that were managed with fertilizer only suggest benefits of manure and compost beyond their N, P and K additions. Similar studies are needed at different locations and with different soil types to evaluate if the results of this study can be repeated elsewhere.
The data from the on-farm studies are currently being summarized.
For further information:
Questions? Contact Quirine Ketterings at 607-255-3061 or qmk2@cornell.edu.